The use of "temporary" wheel-mounted spare tires began in the mid-1970's. This permitted a lowering of spare tire mass and volume as compared to a full size spare pneumatic tire and wheel unit designed for permanent use and capable of meeting all full service passenger vehicle tire and wheel specifications. These so-called "mini-spares", now in widespread use for spare tires, employ a specially-designed pneumatic tubeless tire and specially designed wheel center member of two-piece steel construction on which the tire is mounted. Recognized problems associated with such current pneumatic tire mini-spares include air leakage from the tire while stored in the vehicle trunk-spare compartment which may amount to an unobserved air loss at the rate of 1.5% per month. In addition, although such mini-spares require less trunk space than the full size full service spare tire and wheel and are lighter in weight, there is still a need to further reduce the weight and size of such mini-spares. When such mini-spares are intended to cover a wider range of vehicle wheel and tire diameters, up to for example a 23.875" maximum outer diameter, the weight and volume of current pneumatic tire mini-spares tends to increase dramatically.
Accordingly, there has been much effort in the 1980's to develop a non-pneumatic spare tire (and wheel) design which would solve these problems associated with pneumatic tire mini-spares. One successful result of this effort is the load-bearing non-pneumatic tire ("NPT") disclosed in Palinkas and Page U.S. Pat. No. 4,832,098 issued May 23, 1989, which is incorporated herein by reference. This nonpneumatic spare tire design consists of a rubber tread band bonded to a cast polyurethane or tire body that is, in turn, bonded to a wheel center member. Additional background information on this nonpneumatic tire design is set forth in the article entitled "Non-Pneumatic Tire Technology", appearing in the November, 1990 Issue of Automotive Engineering, Volume 98, No. 11 at pages 29-33, by Scott R. Pajtas.
Aside from the need for improvements in temporary spare tire and wheel units for use as mini-spares, long prior to their advent there has been a general need and desire to improve upon, and indeed, to replace conventional pneumatic tire and wheel assemblies which generally comprise a tubeless pneumatic tire removably mounted on a metal wheel. Typically this two piece construction requires that the manufacture of automotive vehicles purchase wheels from one supplier, and the pneumatic tires from another, which requires these components to be manufactured to specifications to insure compatibility of the tire and wheel components. Thus, purchasing costs, including higher freight costs, and costs of mounting pneumatic tires on the wheels, are maximized to the vehicle manufactured, and hence, to its customers. In addition to weight problems, another disadvantage of the conventional pneumatic tire and wheel assembly resides in the pneumatic tire. Conventional pneumatic tires are subject to air loss when the tire is punctured by stones, metal objects, and other sharp objects which are often found on roadways. This, of course, requires that the automotive vehicle carry a spare pneumatic tire and wheel assembly, which decreases the space available for cargo and adds significantly to the weight of the vehicle. Thus, for many years there has a been a need for a non-pneumatic tire and wheel assembly for use in passenger cars and in off-the-road vehicles. Prior efforts toward this goal are exemplified in the Hampshire U.S. Pat. No. 4,350,196 as well as in the prior art patents cited therein.
Of course, in non-automotive passenger vehicle applications, such as in industrial lift trucks, toy vehicles, heavy duty track laying vehicles, such as tanks and similar earth-mover vehicles, non-pneumatic tire and wheel assemblies have long been used. One recent development useful in (but not limited to) this field is disclosed in the Kindel and Rai U.S. Pat. No. 4,950,030, assigned to Motor Wheel Corporation, the assignee of the present invention. A non-pneumatic tire and wheel unit for motorcycle use is also disclosed in French Patent 2,564,040 (published as European Patent Application 0199911 in November 1986).
Such prior art non-pneumatic tire and wheel assemblies, other than that represented in the aforementioned Palinkas and Page U.S. Pat. No. 4,832,098, have not, so far as is known, achieved the mechanical functions and riding performance characteristics of a conventional pneumatic tire and wheel assembly while also meeting the load and vehicle speed ratings, as well as other performance and safety parameters, required for conventional passenger vehicle pneumatic tire and wheel assemblies (such as those set forth in the Federal Motor Vehicle Safety Standards for passenger car use).